Method for making a multi-layer plastic container having a carbon-treated internal surface

ABSTRACT

A method is provided for making a blow molded multi-layer container having an upper wall portion, including an opening; an intermediate sidewall portion positioned beneath the upper wall portion; and a base portion positioned beneath the intermediate sidewall portion. The container includes (i) a molded inner layer formed from a plastic material, the inner layer having a vertical length and a carbon-treated inner surface; and (ii) a molded outer layer formed from recycled plastic that is substantially coextensive with the inner layer. The recycled outer layer comprises at least 40% by weight of the overall weight of the container, but can comprise more than 90% by weight. In a preferred embodiment, the thickness of the inner and/or outer layers is controllably adjusted along their respective vertical lengths. If functionally desirable, the inner layer and/or outer layer may also include additional barrier materials and/or oxygen scavenging/reacting materials.

TECHNICAL FIELD

[0001] The present invention relates to multi-layered containers. Moreparticularly, the present invention relates to blow molded multi-layerplastic containers having a carbontreated internal surface and a methodfor making such containers.

BACKGROUND ART

[0002] Multi-layer plastic containers are commonly used for packagingitems in a wide range of fields, including food and beverage, medicine,health and beauty, and home products. Plastic containers are known forbeing easily molded, cost competitive, lightweight, and generallysuitable for many applications. Multi-layered containers provide theadded benefit of being able to use different materials in each of thelayers, wherein each material has a specific property adapted to performa desired function.

[0003] Because plastic containers may permit low molecular gases, suchas oxygen and carbon dioxide, to slowly permeate through their physicalconfigurations, the use of plastic containers sometimes proves to beless desirable when compared to containers formed from other lesspermeable materials, such as metal or glass. In most applications, theshelf life of the product contents is directly related to the package'sability to effectively address such molecular permeation. In the case ofcarbonated beverages, such as beer, oxygen in the atmosphere surroundingthe container can gradually permeate inwardly through the plastic wallsof the container to reach inside of the container and deteriorate thecontents. Likewise, carbon dioxide gas associated with the contents maypermeate outwardly through the plastic walls of the container untileventually being released on the outside, causing the carbonatedbeverage to lose some of its savor and possibly become “flat.”

[0004] To address some to the foregoing concerns, plastic containermanufacturers have utilized various techniques to reduce or eliminatethe absorption and/or permeability of such gases. Some of the morecommon techniques include: increasing the thickness of all or portionsof the walls of the container; incorporating one or more barrier layersinto the wall structure; including oxygen-scavenging or reactingmaterials within the walls of the container; and applying variouscoatings to the internal and/or external surface of the container.However, a number of conventional barrier and/or scavenger materialswill not effectively curtail the permeation of both oxygen and carbondioxide over extended periods of time. Moreover, there are usually otherpractical concerns associated with most conventional techniques, mostcommonly, increased material costs and/or production inefficiencies.

[0005] In recent times, the use of plastics has become a significantsocial issue. Recycling has become an increasingly importantenvironmental concern and a number of governments and regulatoryauthorities continue to address the matter. In a number ofjurisdictions, legislation pertaining to minimum recycled plasticcontent and the collection, return, and reuse of plastic containers haseither been considered or has already been enacted. For example, in thecase of plastic containers used to hold consumable items, such as fooditems or beverages, regulations often require a certain content andminimum thickness of the innermost layer that comes in contact with thecontents. Conventional processes, such as co- or multiple-injectionmolding, are often limited as to the amount of recycled plastic that canbe effectively incorporated into the structure of the container.Commonly, the amount of recycled content that can be effectivelyincorporated into conventional co-injection molded containers that aresuitable for food contents is less than 40% of the total weight of thecontainer.

[0006] Therefore, a need exists in the industry for an improvedmulti-layered plastic container having a high recycled content that issuitable for holding carbonated products, such as carbonated beverages,and provides an acceptable level of performance when compared tocommercial containers formed from alternative materials. A further needexists for a method to produce such containers in high volume commercialrates using conventional equipment.

DISCLOSURE OF INVENTION

[0007] Recognizing the problems and concerns associated withconventional multi-layered plastic containers, especially those used tohold carbonated beverages, a multi-layer plastic container havingenhanced gas barrier properties and a high content of recycled plasticis provided. A container constructed in accordance with the principlesof the present invention provides several advantages over thosepreviously available. Such advantages are generally realized through theuse of a both a carbon coating on the internal surface of an innerlayer, wherein the inner layer may have a controllably-varied thicknessand a significant amount of outer recycled content. Furthermore, theimproved container can be produced using conventional processingtechniques and manufacturing equipment.

[0008] An important aspect of the present invention is its ability toincorporate the functional benefits of an exceptionally thin, but veryeffective, barrier with the functional and commercial benefitsassociated with having an outer layer comprised a significant amount ofrecycled plastic content. Further, the ease in subsequently recycling acontainer produced in accordance with the principles of the presentinvention make the practice of the invention extremely advantageous.Moreover, the present invention provides the additional advantage ofpermitting the manufacturer to controllably vary the materialpositioning and wall thickness at any given location along the verticallength of the inner and/or outer layers of the container.

[0009] In accordance with the principles of the present invention, ablow molded multi-layer container is provided having an upper wallportion, an intermediate sidewall portion positioned beneath the upperwall portion, and a base portion positioned beneath the intermediatesidewall portion, the base portion being adapted to dependently orindependently support the container. The container includes (i) a moldedinner layer formed from a plastic material, the inner layer having avertical length and a carbon-treated inner surface; and (ii) a moldedouter layer formed from recycled plastic that is substantiallycoextensive with the inner layer. The recycled outer layer comprises atleast 40% by weight of the overall weight of the container, but cancomprise more than 90% by weight, depending upon the needs of theapplication. In a preferred embodiment, the thickness of the innerand/or outer layers is controllably adjusted along their respectivevertical lengths. If functionally desirable, the inner layer and/orouter layer may also include additional barrier materials and/or oxygenscavenging/reacting materials.

[0010] Other and further advantages and novel features of the inventionare readily apparent from the following detailed description of the bestmode for carrying out the invention when taken in connection with theaccompanying drawings, wherein, by way of illustration and example,embodiments of the present invention are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is an elevation view of a container in accordance with theprinciples of the present invention.

[0012]FIGS. 1A, 1B and 1C are cross-sectional and enlarged views ofvarious areas of the container wherein the relative thicknesses of thelayers forming the container are illustrated.

[0013]FIG. 2 is a partially broken away elevation view of one example ofa multi-layer preform.

[0014]FIG. 3 is a partially broken away elevation view of anotherexample of a multi-layer preform.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Referring now to the drawings in detail, wherein like referencenumerals and letters designate like elements, there is shown in FIG. 1an elevational view of a container 10 constructed in accordance with theprinciples of the present invention. Container 10 typically includes anupper wall portion 12, including an opening 13; an intermediate sidewallportion 14 positioned beneath the upper wall portion 12; and a baseportion 16 positioned beneath the intermediate sidewall portion 14. Thebase portion 16 is adapted to support the container 10 eitherdependently, i.e., where another object such as a base cup (not shown)is used, or independently, i.e., where no other objects are needed tostand the container upright on a generally flat surface. In a preferredembodiment, the container 10 is supported by a freestanding base formedby a plurality of integrally formed feet 18, such as those illustratedin FIG. 1.

[0016] Referring to FIGS. 1A-1C, which represent enlarged detailed viewsof areas 1A, 1B and 1C, respectively, of FIG. 1, the container 10includes (a) a molded inner layer 20, having a vertical length and aninner surface 22; (b) a molded outer layer 24; and (c) a centralvertical axis A. The inner surface 22 of the molded inner layer 20 is atleast partially coated with a thin layer or film of carbon 26. Whilecomplete encapsulation of the inner layer 20 by the outer layer 24 isnot required, it is preferred that the molded outer layer 26 issubstantially coextensive with the inner layer 20 and providesstructural support to the walls of the container 10.

[0017] The molded inner layer 20 is comprised of a thermoplasticmaterial. The following resins may be used as plastic materials for theinner layer 20: polyethylene resin, polypropylene resin, polystyreneresin, cycloolefine copolymer resin, polyethylene terephthalate resin,polyethylene naphthalate resin, ethylene-(vinyl alcohol) copolymerresin, poly-4-methylpentene-1 resin, poly (methyl methacrylate) resin,acrylonitrile resin, polyvinyl chloride resin, polyvinylidene chlorideresin, styrene-acrylo nitrile resin, acrylonitrile-butadien-styreneresin, polyamide resin, polyamideimide resin, polyacetal resin,polycarbonate resin, polybutylene terephthalate resin, ionomer resin,polysulfone resin, polytetra fluoroethylene resin and the like. Whenfood product contents are involved, the inner layer 20 is preferablyformed from virgin polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), and/or blends of polyethylene terephthalate andpolyethylene naphthalate. However, other thermoplastic resins,particularly those approved for contact with food products, may also beused.

[0018] The molded outer layer 24 is comprised of a recycled plasticmaterial, including the plastics set forth in the preceding paragraph,but is commonly formed from recycled polyethylene terephthalate (PET).However, the invention is not limited to a particular type of recycledplastic and other recycled plastic materials may be used.

[0019] In a preferred embodiment, the inner layer 20 has a wallthickness, taken along its vertical length, that is in the range of 0.5mil to 5 mil (0.0127 mm to 0.127 mm) and more preferably between 1 to 2mils (0.0254 mm to 0.0508 mm). In some instances, such as where foodproduct contents are involved, a minimum thickness requirement for theinner layer 20 may be specified and must be met. As illustrated in FIG.1 and FIGS. 1A, 1B and 1C, the thickness of the inner layer may bevaried along the vertical length. In this manner, different portions ofthe container 10 can have variably controlled thickness along thevertical length, providing improved material usage and increased designflexibility. For instance, the thickness of the inner layer 20positioned at the upper portion 12 (such as shown in FIG. 1A) can bethinner than the intermediate sidewall portion 14 (such as shown in FIG.1B). Likewise, the thickness of the inner layer 20 at the base wallportion 16 (such as shown in FIG. 1C) can be thicker than the thicknessof the same layer in the intermediate sidewall portion 14 (such as shownin FIG. 1B).

[0020] In keeping with an aspect of the present invention, the innerlayer comprises less than 0.60 by weight of the total weight of thecontainer 10, preferably less than 0.30 of the total weight of thecontainer 10, and more preferably, less than about 0.15 of the totalweight of the container 10. The ability of the present invention toutilize an exceptionally thin inner layer 20 -- particularly whencompared to other conventional multi-layer containers -- can providesignificant economic advantages and incentives, especially in instancesin which virgin material is more costly and/or scarce than recycledmaterial.

[0021] As mentioned earlier, the inner surface 22 of the inner layer 20is coated with a thin layer of carbon 26 which provides enhanced barrierproperties to the container 10. In a preferred embodiment, the carboncoating 26 is comprised of a highly hydrogenated amorphous carbon thatis doped with nitrogen. The thickness of the carbon coating 26 is lessthan about 10 μm and the weight of the coating 26 is less than about{fraction (1/10,000)}^(th) of the total weight of the container. Animportant feature of the present invention is that only about 3 mg ofthe carbon coating 26 is needed to treat a 500 cc plastic container.Further, despite the notable thinness of the carbon coating 26, theamount of barrier protection afforded is quite significant and theprotection from permeation of oxygen and carbon dioxide is favorablewhen compared with the protection found in metal cans and glass bottles.Initial tests have shown that the barrier provided in connection withthe present invention against oxygen permeation can be more than thirtytimes better than that of a container formed from untreated PET; thebarrier provided against carbon dioxide permeation can be more thanseven times better than that of a container formed from untreated PET;and the barrier provided against the migration of total aldehydes can bemore than 6 times better than untreated PET.

[0022] The molded outer layer 24 comprises at least about 0.40 by weightof the total weight of the container 10, but can comprise more than 0.90by weight of the total weight of the container 10 for certainapplications. In a preferred embodiment, the outer layer 24 has a wallthickness, taken along its vertical length, that is in the range of 6 to23 mils (0.1524 mm to 0.5842 mm). As illustrated in FIG. 1 and FIGS. 1A,1B and 1C, the thickness of the outer layer can also be separately andindependently varied along its vertical length. In this manner,different portions of the container 10 (taken perpendicular to thecentral vertical axis A) can have different inner layer thicknesses,different outer layer thicknesses, and/or different overall thicknessmeasurements, all by design. For instance, the thickness of the moldedouter layer 24 positioned at the upper portion 12 (such as shown in FIG.1A) can be much thicker than the intermediate sidewall portion 14 (suchas shown in FIG. 1B). Likewise, the thickness of the outer layer 24 atthe base wall portion 16 (such as shown in FIG. 1C) can be thicker thanthe thickness of the same layer in the intermediate sidewall portion 14(such as shown in FIG. 1B). Because the molded outer layer 24 isgenerally comprised of a less expensive plastic material that does notdirectly contact the contents of the container 10, a less expensivematerial can be used to form a number of the structural integralcomponents for the container, such as the neck flange 30 and outerthreads 32 shown in FIG. 1.

[0023] While it is often unnecessary—and can complicate the recyclingprocess—in special applications, the inner layer 20 and/or outer layer24 may further include additional barrier materials and/or oxygenscavenging/reacting materials (not shown) that are commonly known in theart. Examples of some of the more commonly used barrier materialsinclude saran, ethylene vinyl alcohol copolymers (EVOH), andacrylonitrile copolymers, such as Barex. The term saran is used in itsnormal commercial sense to contemplate polymers made for example bypolymerizing vinylidene chloride and vinyl chloride or methyl acrylate.Additional monomers may be included as is well known. Vinylidenechloride polymers are often the most commonly used, but other oxygenbarrier materials are well known. Oxygen-scavenging materials caninclude materials marketed for such a purposes by several large oilcompanies and resin manufacturers. A specific example of such a materialis marketed under the trade name AMOSORB and is commercially availablefrom the Amoco Corporation.

[0024] Another significant advantage of the present invention is itsability to provide significant barrier properties, incorporate a highcontent of recycled plastic material, and be advantageous to present dayrecycling. The inner layer 20 and outer layer 24 are both comprised ofplastic material and can be readily recycled. Unlike a number of otherbarrier materials often used in connection with multi-layer containers,which can be difficult to separate, the carbon coating 26 of the presentinvention has no impact on the recycling of the plastic materials ofwhich the container 10 is comprised.

[0025] The present invention includes the additional advantage of beingable to provide a container 10 with enhanced barrier properties that canbe used for holding food products. Plastic containers having an innersurface treated with an amorphous carbon film have been approved forcontact with food products from the Technische National Onderzoek, thestandards organization accredited by the European Economic Community.The approval of the United States Food and Drug Administration (USFDA)is currently in process.

[0026] The container 10 of the present invention may be formed by any ofseveral known processing techniques which permit the manufacture of amulti-layer blow molded container 10 having a plastic molded inner layer20 and a relatively thick molded outer layer 24 of recycled plastic. Ina preferred embodiment, the multi-layer container 10 is formed via ablow molding operation involving a multi-layer preform 34, such as theone generally depicted in FIG. 2. Although not a required feature, thepreform 34 may include a neck flange 30 (for handling purposes) andouter threads 32 (to secure a closure) that correspond to the samefeatures shown in FIG. 1. After the blow molding of the container 10,but some time before the filling operation, the inner surface 24 of theinner layer 20 of the container 10 is carbon-treated as furtherdiscussed below.

[0027] In a first preferred embodiment, the preform 34 is produced byextrusion molding an inner layer 20′ and injection molding an outerlayer 24′. The inner layer 20′ and outer layer 24′ of the preform 34correspond to the inner layer 20 and outer layer 24 of the container 10.Extrusion of the inner layer 20′ of the preform allows the manufacturerproduce a thinner layer than is generally possible using conventionalinjection molding or co-injection processes. For example, the innerlayer of an extrusion molded multi-layer preform 34 may be made as thinas 15-20 mils (0.381 mm to 0.508 mm) or less. Conversely, it isdifficult, if not impossible, to reliably injection mold an inner layerhaving a comparable thickness profile. Further, an extrusion orco-extrusion process permits the manufacturer to readily vary thethickness of material being extruded along the length of the extrudate.Variations in the thickness of the inner layer is desirable for severalreasons which include aesthetics, efficient material use and reducedcosts, and variable strength requirements.

[0028] The outer layer 24′ of the preform 34 is formed from a recycledplastic material and, in accordance with the present invention, issubstantially thicker than the inner layer 20′. The outer layer 24′ canbe injection molded or compression molded over the inner layer 20′,although injection molding is generally preferred. Such over-moldingprocesses further permit the formation of a neck flange 30 and outerthreads 32.

[0029] In a second preferred embodiment, the multi-layer preform 34 isproduced by thermoforming a thin sheet of plastic material and formingthat sheet into what will become the inner layer 20′ of the preform 34.The process of thermoforming permits the formation of a preform 34 witha very thin inner layer 20′. In fact, minimum wall thicknesses of 3 mil(0.0762 mm) or less are possible. As in the case of an extruded innerlayer 20′, once the inner layer 20′ of the preform 34 is formed, theouter layer 24′ of recycled plastic can be injection or compressionmolded over the inner layer 20′ to provide a multi-layer preform 34.FIG. 3 is a representative example of a preform 34 formed from athermoformed inner layer 20 and injection molded outer layer 24.Preforms 34 formed in accordance with the principles of such secondpreferred embodiment are generally better suited for applications thatrequire a wider opening 13 or dispensing mouth.

[0030] The multi-layer container can then be blown using conventionalblow molding operations. Because the preform 34 will be stretched and“thinned-out” during the subsequent blow molding process, the thicknessof the preform 34 - at portions corresponding to like portions of theblown container - will inherently be somewhat thicker. In fact, thethickness of the various portions of the preform 34 are typicallydesigned to take into account the amount of stretch and hoop expansionnecessary to form the thickness profile desired in the final container10. For clarity, hereinafter, the multi-layer containers having innerand outer layers 20,24 that have not been carbon-treated will bedesignated as 10′ to distinguish them from containers 10 in which theinner surface 22 has been carbon coated.

[0031] After a container 10′ having an inner layer 20 and outer layer 24are produced, a carbon coating is formed on at least a portion of theinner surface 22 of the inner layer 20. The carbon coating 26 does nothave to be immediately applied to the container, however, it isgenerally more efficient to apply the coating 26 promptly after thecontainer 10′ has been blown and is within an appropriate temperatureprofile.

[0032] In a preferred embodiment, the blown multi-layer containers 10′are removed from a conventional high-speed rotary blow-molding machineand subsequently transferred, directly or indirectly (i.e., via anintermediate handling steps), to an apparatus for applying a carboncoating 26 to the containers 10′. In high-speed production applications,the carbon-coating apparatus will typically also be of the rotary type.An example of such an apparatus that can be used to apply the carboncoating to the inner surface 22 of the containers 10′ is available fromSidel of Le Havre, France and is commercially marketed under the “ACTIS”trade name.

[0033] A method for carbon-coating multi-layer containers 10′ is nextdescribed in further detail. In accordance with a preferred method forcarbon coating the inner surface 22 of the container 10,′ a conventionalcarbon-coating or carbon-treating apparatus having rotary kinematics anda central vertical axis is provided. The carbon-coating apparatusgenerally rotates about its central vertical axis in a first rotationaldirection, e.g. counterclockwise, at a fairly high rotational speed. Ablow-molding machine, or other rotary container transfer mechanism,located generally in close proximity to the carbon-coating apparatusfunctions as the source of containers 10′ for subsequent carbon-coatingtreatment. To facilitate the transfer, the rotary container transfermechanism rotates in a direction opposed to the rotational direction ofthe carbon-coating apparatus—e.g., clockwise—and the multi-layercontainers 10′ are mechanically shifted from the container transfermechanism to the carbon-coating apparatus. Although not required for thepractice of the present invention, the container 10′ preferably includesa neck flange 30 or other physical means for at least partiallysupporting the container 10′ during the mechanical transfer process.

[0034] As the containers 10′ are transferred from the transfer mechanismto the carbon-coating apparatus, the containers 10′ are preferably heldby the upper portion 12 in an upright orientation with the opening 13generally facing upwardly. If desired, a vacuum can also be generatedand used to support or partially support the container 10′. During thetransfer process, the individual containers 10′ are received by areceiving mechanism which is part of the carbon-coating apparatus. Thereceiving mechanism revolves around the central axis of thecarbon-coating apparatus, grasps or secures the container 10′, and sealsthe opening 13 of the upper portion 12 of the container 10′, much like alid. When properly positioned over and abutting the opening 13, thereceiving mechanism produces a tight to “airtight” seal over thecontainer 10′.

[0035] The receiving mechanism includes at least two aperturespositioned above the opening 13 of the container 10′ that are used forthe introduction and removal of gases from the inside of the container10′. A first aperture in the receiving mechanism is in communicationwith a vacuum source, such as a vacuum pump. After the receivingmechanism has securely sealed the opening 13, the air within thecontainer 10′ is discharged through the first aperture by means of avacuum. It is desirable that degree of vacuum falls within a range ofabout 10⁻² to 10⁻⁵ torr, so as to shorten the discharge time for avacuum and saves necessary energy therefor. With a lower degree ofvacuum of over 10⁻² torr, impurities in the container are muchincreased, on the other hand, with a higher degree of vacuum under 10⁻⁵torr, increased time and a large energy are needed to discharge the airin the container 10′.

[0036] Once the air inside the container 10′ has been evacuated, thecontainer 10′ is subsequently filled or “charged” with a raw gas thatwill be used in the formation of the carbon coating 26. The flow rate ofthe raw gas is preferably within a range from about 1 to 100 ml/min.Preferably, the diffusion of the raw gas within the container 10′ isenhanced by providing an extension, such as a tube having a plurality ofblowing openings. In accordance with one embodiment, an extension entersinside of the container 10′ through the second aperture some time afterthe opening 13 is sealed and the extension extends to within about 25.4mm to 50.8 mm (1.0 in. - 2.0 in.) of the lowermost portion of thecontainer 10′.

[0037] The raw gas may be comprised of aliphatic hydrocarbons, aromatichydrocarbons, oxygen containing hydrocarbons, nitrogen containinghydrocarbons, etc., in gaseous or liquid state at a room temperature.Benzene, toluene, o-xylene, m-xylene, p-xylene and cyclohexane eachhaving six or more than six carbons are preferable. The raw gases may beused singularly, but a mixture of two or more than two kinds of rawgases can also be used. Moreover, the raw gases may be used in the stateof dilution with inert gas such as argon and helium.

[0038] At some point after the container 10′ has been received by thereceiving mechanism of the carbon-coating apparatus, the container 10′is inserted into a cylinder or other hollow space provided toaccommodate the container 10′. In the preferred embodiment, thecarbon-coating apparatus includes a plurality of hollow cylinders thatrotate in the same direction as, and in synchronization with, thereceiving mechanism. It is further preferred that the receivingmechanism that retains and seals the opening 13 of the container 10′also functions to cover the cylinder.

[0039] After the supply of the raw gas into the container, energy isimpressed upon the container 10′ from a high frequency electric energysource, such as a micro-wave-producing device. The impression of theelectric power generates plasma, and causes extreme molecular excitationionization and a carbon coating 26 to be formed on the inner surface 22of the container 10′.

[0040] While the foregoing method illustrates one process for forming acarbon coating 26 on the inner surface 22 of a container 10′, otherconventional methods can also be used successfully. For instance, theplastic container 10′ could instead be inserted and accommodated withinan external electrode and have an internal electrode positioned withinthe container 10′. After the container 10′ is evacuated and is chargedwith raw gas supplied through the internal electrode, electric power issupplied from the high frequency electric source to the externalelectrode. The supply of electric power generates plasma between theexternal electrode and the internal electrode. Because the internalelectrode is earthed, and the external electrode is insulated by theinsulating member, a negative self-bias is generated on the externalelectrode, so that carbon film is formed uniformly on the inner surfaceof the container along the external electrode.

[0041] When the plasma is generated between the external electrode andthe internal electrode, electrons are accumulated on the inner surfaceof the insulated external electrode to electrify negatively the externalelectrode, to generate negative self-bias on the external electrode. Atthe external electrode, a voltage drop occurs because of the accumulatedelectrons. At this time, carbon dioxide as the carbon resource exists inthe plasma, and positively ionized carbon resource gas is selectivelycollided with the inner surface 22 of the container 10′ which isdisposed along the external electrode, and, then, carbons close to eachother are bonded together thereby to form hard carbon film comprisingremarkably dense coating on the inner surface 22 of the container 10′.

[0042] The thickness and uniformity of the carbon coating 26 can bevaried by adjusting the output of high frequency; the pressure of theraw gas in the container 10′; the flow rate for charging the container10′ with gas; the period of time during which plasma is generated; theself-bias and kind of raw materials used; and other like variables.However, the thickness of the carbon coating 26 is preferably within arange from 0.05 to 10 μm to obtain the effective suppression of thepermeation and/or absorption of the low molecular organic compound andthe improved gas barrier property, in addition to an excellent adhesionto plastic, a good durability and a good transparency.

[0043] Although certain preferred embodiments of the present inventionhave been described, the invention is not limited to the illustrationsdescribed and shown herein, which are deemed to be merely illustrativeof the best modes of carrying out the invention. A person of ordinaryskill in the art will realize that certain alternatives, modifications,and variations will come within the teachings of this invention and thatsuch alternatives, modifications, and variations are within the spiritand the broad scope of the appended claims.

What is claimed is:
 1. A method of manufacturing a multi-layer containercoated with a carbon coating, which comprises: providing a multi-layeredcontainer including an upper wall portion having an opening, anintermediate side wall portion positioned beneath the upper wallportion, a base portion positioned beneath the intermediate wallportion, and a central vertical axis, said container further including aplastic inner layer having a vertical length and an inner surface and anouter layer including recycled plastic having a vertical length and aninner surface that is substantially coextensive with the inner layer,wherein the inner layer has a thickness that is between 0.022 and 0.833the thickness of the outer layer taken at the same point along theirvertical lengths, the outer layer comprises at least 0.40 of the overallweight of the container, and the outer layer is in a contactingrelationship with the inner layer along substantially the entire innersurface of the outer layer; enclosing the multi-layered container withina hollow space provided to accommodate the container; discharging theair within the container and creating a vacuum; charging the internalvolume of the container with raw gas; and forming a carbon coating fromsaid raw gas on the inner surface of the inner layer of the container.2. A method according to claim 1, wherein the multi-layered container isformed by extruding a plastic sleeve from a thermoplastic material;injection molding an outer layer over the sleeve to form a preform; andblow molding the preform to form a multi-layer container.
 3. A methodaccording to claim 1, including the step of varying the thickness of theinner layer along its vertical length.
 4. A method according to claim 1,including providing that the inner layer includes a material selectedfrom the group consisting of a barrier material, an oxygen-scavengingmaterial, and a material that is a combination of a barrier and anoxygen-scavenger.
 5. A method according to claim 1, including chargingthe internal volume of the container with raw gas selected from thegroup consisting of aliphatic hydrocarbons, aromatic hydrocarbons,oxygen containing hydrocarbons, and mixtures of two or more of suchgases.
 6. A method according to claim 1, wherein the formation of thecarbon coating on the inner surface of the container is induced by ahigh frequency electric source.
 7. A method according to claim 6,including providing that the high frequency electric source includes aninternal electrode and an insulated external electrode for generatingnegative self-bias.
 8. A method according to claim 1, wherein theformation of carbon coating on the inner surface of the container isinduced by a microwave.
 9. A method according to claim 1, includingproviding that the outer layer comprises at least 0.90 by weight of theoverall weight of the container.
 10. A method according to claim 1,including the step of forming the carbon coating with a substantiallyuniform thickness.
 11. A method according to claim 1, includingproviding that the inner layer has a wall thickness taken along itsvertical length that is within the range of about 0.5 mil to about 5 miland the outer layer has a wall thickness taken along its vertical lengththat is within the range of about 6.0 mils to about 23 mils.
 12. Amethod according to claim 1, including forming a carbon coating that isamorphous.
 13. A method according to claim 1, including the step offorming the carbon coating has a thickness that is less than 10 μm. 14.A method according to claim 1, including the step of forming the carboncoating with the weight of the carbon coating being less than about{fraction (1/10,000)}^(th) of the total weight of the container.
 15. Amethod according to claim 1, wherein the thickness of the inner layerand outer layer are controllably varied with respect to one another. 16.A method according to claim 1, wherein the step of forming the carboncoating on the inner surface of the inner layer of the containerincludes the rotation of the container about the central vertical axis.17. A method according to claim 16, wherein the rotation includeshigh-speed rotation.
 18. A method according to claim 1, including atransferring process for handling the container.
 19. A method accordingto claim 18, wherein the transferring process includes rotation of thecontainer.
 20. A method according to claim 16, including a transferringprocess for handling the container with rotation of the container duringthe transferring process, the rotation of the transfer process is in adirection opposed to the direction of rotation of the container duringthe carbon coating of the inner surface of the inner layer.
 21. A methodaccording to claim 1, including the step of providing that a receivingmechanism seals the opening of the container to produce a substantiallyair-tight seal prior to the complete discharging of the air within thecontainer.
 22. A method according to claim 21, including the step ofproviding that the receiving mechanism is revolved around the centralaxis of the container and secures the container.
 23. A method accordingto claim 21, including the step of providing that the receivingmechanism includes at least two apertures for the communication ofgases.
 24. A method according to claim 21, including the step ofproviding that the receiving mechanism is in communication with a vacuumsource.
 25. A method according to claim 1, wherein the vacuum created iswithin the range of about 10⁻² to 10⁻⁵ torr.
 26. A method according toclaim 1, including the step of providing that the flow rate for chargingthe internal volume of the container with raw gas is within the rangefrom about 1 to 100 ml/min.
 27. A method according to claim 1, includingusing high frequency to charge the gas and to control the thickness ofthe carbon coating on the inner surface of the inner layer.